SCCR of panels with series ratings

[Tainted]

We all know that the SCCR of the panel depends on the lowest interrupting rating of the device installed inside the panel.

Suppose I have a standalone 600 amp(200kAIC) main feeding a panel with 20 amp (10kAIC), 40 amp (42kAIC) and 60 (75kAIC) amp branch breakers...

The 60 amp branch breaker series rate with the 600 amp main at 125kAIC

The 40 amp branch breaker series rate with the 600 amp main at 90kAIC

The 20 amp branch breaker series rate with the 600 amp main at 50kAIC

My question is:

Is the SCCR of the panel based on the lowest interrupting rating of the overcurrent device installed (10kAIC) or is it based on the lowest series rating (50kAIC)? In this example, what is the SCCR of the panel?

 

[electrofelon]

I would say it doesn't actually matter. I have expressed this before, but I don't like the way SCCR "changes" based on the OCPD installed. Most logical to me is that SCCR is what it is and doesn't change regardless of what OCPD is installed. Of course you couldn't utilize that "extra" SCCR if the AIC of an OCPD is less as that would be your "weakest link". But for whatever reason, the industry has chosen to use the former approach.

Anyway, I think by the industry silly method, the SCCR of you panel would be 50. The SCCR follows along with the series ratings.

One more thing:. I assume those numbers are just made up yes? I've actually never seen series ratings like that, where the value is somewhere between the upstream and downstream ratings. It's always the full value of the upstream device or nothing. If you can provide me with a counter example I would be interested to see it.

One final thing, note that I think you will not find a series rating of a 600 amp frame and regular 10K AIC breaker (the 20A in your example). If you go to 22KAIC branch however, you will usually get a zillion more options, even up to a 1200A upstream device at 100k, or a 600A at 200k for some Siemens examples.

 

[Tainted]

I would say it doesn't actually matter. I have expressed this before, but I don't like the way SCCR "changes" based on the OCPD installed. Most logical to me is that SCCR is what it is and doesn't change regardless of what OCPD is installed. Of course you couldn't utilize that "extra" SCCR if the AIC of an OCPD is less as that would be your "weakest link". But for whatever reason, the industry has chosen to use the former approach.

Anyway, I think by the industry silly method, the SCCR of you panel would be 50. The SCCR follows along with the series ratings.

One more thing:. I assume those numbers are just made up yes? I've actually never seen series ratings like that, where the value is somewhere between the upstream and downstream ratings. It's always the full value of the upstream device or nothing. If you can provide me with a counter example I would be interested to see it.

One final thing, note that I think you will not find a series rating of a 600 amp frame and regular 10K AIC breaker (the 20A in your example). If you go to 22KAIC branch however, you will usually get a zillion more options, even up to a 1200A upstream device at 100k, or a 600A at 200k for some Siemens examples.

I think this UL article agrees with you that the panel should be rated 50kAIC in my example.

You can see a diagram in the last page with 65kAIC breaker series rating with 10kAIC breakers and that the panel is now rated 65kAIC even though there are 10kAIC breakers in them:

https://japan.ul.com/wp-content/uploads/2014/04/ul_PanelboardShortCircuitRatings.pdf

Also I made those numbers up just to make an example because I’m doing a project that involves doing this.

Also some of those 3VA MLAS type siemens breakers have 100kAIC ratings and series rate at 85kAIC with some other branch breakers.

For example 3VA54 MLAS (100kAIC) main breakers series rate with QPH (22kAIC) at 85kAIC. Unless I am using this chart incorrectly.

I am using this chart:

https://digitalcontentcenter.compas.siemens-info.com/SIE_CR_3VA_SeriesRatingsUL.xlsx

 

[electrofelon]

Also some of those 3VA MLAS type siemens breakers have 100kAIC ratings and series rate at 85kAIC with some other branch breakers.

For example 3VA54 MLAS (100kAIC) main breakers series rate with QPH (22kAIC) at 85kAIC. Unless I am using this chart incorrectly.

I am using this chart:

https://digitalcontentcenter.compas.siemens-info.com/SIE_CR_3VA_SeriesRatingsUL.xlsx

Hmmm, the MLAS class is an 85k rating not 100. HLAS would be 100k Where did you see the MLAS rated as 100k?

I looked through a bunch of the other 3VA breakers and could not find a counter example to my theory with any of them. I did find an HEAS shown with a 100k series rating, and in the catalog that breaker is shown as 150KAIC on one page, and 100KAIC on another page, so I think that one is just a typo.

 

[Tainted]

Hmmm, the MLAS class is an 85k rating not 100. HLAS would be 100k Where did you see the MLAS rated as 100k?

I looked through a bunch of the other 3VA breakers and could not find a counter example to my theory with any of them. I did find an HEAS shown with a 100k series rating, and in the catalog that breaker is shown as 150KAIC on one page, and 100KAIC on another page, so I think that one is just a typo.

Actually you are right, I looked through the chart and mixed up between MLAS and HLAS.

It's kind of scary how there are typos in these things. There's no room for typos for stuff like that...

 

[electrofelon]

Actually you are right, I looked through the chart and mixed up between MLAS and HLAS.

It's kind of scary how there are typos in these things. There's no room for typos for stuff like that...

The 3VA line is relatively new and I am not very familiar with them, but I find the part number system, particularly this interrupting level coding to be super confusing

 

[Tainted]

The 3VA line is relatively new and I am not very familiar with them, but I find the part number system, particularly this interrupting level coding to be super confusing

Haha, agreed. I'm giving these a try though, speced a switchboard with these in them.

What would be your alternative?

 

[electrofelon]

Haha, agreed. I'm giving these a try though, speced a switchboard with these in them.

What would be your alternative?

Well I don't have anything against them other than the confusing nomenclature, and a big part of his probably just it being new to me.
not saying I'm going to necessarily choose an alternative just because of that. Once I get a little more familiar with the part numbering I'm sure it will be smoother sailing!

 

[Tainted]

Well I don't have anything against them other than the confusing nomenclature, and a big part of his probably just it being new to me.
not saying I'm going to necessarily choose an alternative just because of that. Once I get a little more familiar with the part numbering I'm sure it will be smoother sailing!

But out of curiosity, what did you use before the 3VA breakers that your familiar with?

 

[electrofelon]

But out of curiosity, what did you use before the 3VA breakers that your familiar with?

Mostly BL and BQD for panelboard breakers, and frequently Siemens QR (250A) frame. I haven't needed anything too large in the past as most of the larger services I did (1000-1200A) were before the MLO ban so most of those were P4 or P5 panelboards with 6 QR's and no main. I did a generator retrofit later at one of those and put a 600A LXD in to feed the ATS. I got that used to save my client some money, and just got the bus kit from Siemens. Did have to get a new P3 panel for generator distribution after the ATS, and that did have a 400A 3VA in it, but IIRC I just let Siemens spec that specific breaker, I just told them I needed a 400 amp.

 

[Jraef]

What’s happening at Siemens is what began when I was working there, we US and Canada employees called it the “NIH Syndrome” for “Not Invented Here”, meaning Germany. Up until around 2005, the breakers being sold here by Siemens were all still the original ITE breakers, virtually unchanged and backward compatible. The entire 3VL line of breakers from Germany were available to sell to OEMs and such but not compatible with the existing ITE panel designs. So over the years they have been introducing modified versions of the German 3VL breakers that will work and have been slowly “NIH-ing” the ITE breakers. I would expect them to continue making the older ITE styles for residential plug-in panels into the future because of the installed base, but I think bolt-in breakers in the ITE designs will fall by the wayside.

 

[electrofelon]

but I think bolt-in breakers in the ITE designs will fall by the wayside.

They do currently have "panelboard" breakers (1" wide per pole bolt ons) in the 3VA line, but I have never bought one or seen in the wild. Are you saying u think they will ultimately discontinue the BL (your standard 240 bolt on line) and BQD (your standard 277/480 bolt on line) for the 3VA line?